linux-kernel - Re: [RFC PATCH v1] can: m_can: m_can_read_fifo: fix memory leak in error branch

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Date:   Fri, 29 Oct 2021 13:34:05 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Vincent Mailhol <mailhol.vincent@...adoo.fr>
Cc:     linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Matt Kline <matt@...bashing.io>,
        Sean Nyekjaer <sean@...nix.com>,
        Chandrasekar Ramakrishnan <rcsekar@...sung.com>
Subject: Re: [RFC PATCH v1] can: m_can: m_can_read_fifo: fix memory leak in
 error branch

On 27.10.2021 03:09:09, Vincent Mailhol wrote:
> In m_can_read_fifo(), if the second call to m_can_fifo_read() fails,
> the function jump to the out_fail label and returns without calling
> m_can_receive_skb(). This means that the skb previously allocated by
> alloc_can_skb() is not freed. In other terms, this is a memory leak.
> 
> This patch adds a new goto statement: out_receive_skb and do some
> small code refactoring to fix the issue.

This means we pass a skb to the user space, which contains wrong data.
Probably 0x0, but if the CAN frame doesn't contain 0x0, it's wrong. That
doesn't look like a good idea. If the CAN frame broke due to a CRC issue
on the wire it is not received. IMHO it's best to discard the skb and
return the error.

Marc

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